Analysis of the Global Water Vapor Distribution with COSMIC Radio Occultation Observations

Abstract

Water vapor is one of the most important greenhouse gases in the Earth’s atmosphere. It plays a crucial role in the energy and hydrological cycles of the Earth’s climate system. In this study, we compare the wet profiles derived from Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) radio occultation (RO) during 2009 with those from radiosondes. The results show that the specific humidity profiles derived from COSMIC RO observations agree well with those from radiosonde observations. In addition, the global distribution of water vapor derived from COSMIC RO shows that the gradient variation from low latitude to high latitude is distinct except in some special areas, such as the Sahara desert of North Africa, which reflects the impacts of upward and downward branches of the Hardley cell, Ferrel cell and the polar circulation during NH summer and NH winter. The contrast between dry and moist regions is most distinct in the tropics. A pair of zonal circulations rotating in the opposite direction can be seen between the Pacific Ocean and India Ocean and between Africa and Atlantic Ocean, respectively. In NH summer, double InterTropical Convergence Zones (double ITCZs) occur over the western Pacific.